In all Valve's games you can bind whatever key you want to whatever function you want, and even write complex scripts to automate actions like building a sentry gun in TF2. Nowadays things like the rate of fire is hard limited so you can't really cheat much with it, unless you use an external utility that can get your Steam account banned from online play.

To be fair, a script for building a sentry gun would be far from complex. If it goes to the blueprint state it's saving you one button press. If the script drops the sentry in front of you then you lose your chance to rotate it.